# Chem 3A

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Half-Life

A radium-226 sample initially contains 0.112 mol. How much radium-226 is left in the sample after 6400 years? The half-life of radium-226 is 1600 years.

• Chem 3A -

6400 years is 4 half-lives. The amount remaining is
0.112 mol * (1/2)^4
= 0.112/16 = 0.007 mol

• Chem 3A -

0.014

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